Correction of astigmatism in a Czerny-Turner spectrograph using a plane grating in divergent illumination

Bates, B.; McDowell, M. W.; Newton, Andrew

doi:10.1088/0022-3735/3/3/310

Cited by 26 publications

(7 citation statements)

References 17 publications

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“…It was important to minimize the astigmatism of the CZT as much as possible at the exit slit plane. This effect is well described in Dalton (1966), Bates et al (1970) and Austin et al (2009). One simple method was to compensate for this by reducing the distance between the input entrance slit and the collimating mirror so that the grating is under divergent illumination (Bates et al 1970).…”

Section: Opticsmentioning

confidence: 97%

“…This effect is well described in Dalton (1966), Bates et al (1970) and Austin et al (2009). One simple method was to compensate for this by reducing the distance between the input entrance slit and the collimating mirror so that the grating is under divergent illumination (Bates et al 1970). In this condition, diffraction in the tangential plane upon reflection from the grating introduces an astigmatism that can compensate for the off-axis reflections from the spherical optics.…”

Section: Opticsmentioning

confidence: 99%

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The Far Ultra-Violet Imager on the Icon Mission

et al. 2017

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ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N 2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O + ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny-Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with

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Section: Opticsmentioning

confidence: 97%

Section: Opticsmentioning

confidence: 99%

The Far Ultra-Violet Imager on the Icon Mission

et al. 2017

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“…[1][2][3][4][5] Most of them are based on an elaborate rearrangement of optical components in the spectrometer. In our study, instead, the spectrometer is equipped with a set of optics in front of the entrance slit to adjust the different focal points on the sagittal and meridional planes.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution measurement of atomic radiation with an astigmatism-corrected Czerny-Turner-type spectrometer in the Large Helical Device

Goto

Morita

2006

Review of Scientific Instruments

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Emission lines in the visible/UV wavelength ranges are observed with 80 lines of sight which cover an entire poloidal cross section of the plasma in the Large Helical Device. The emitted light is received with optical fibers having 100 m diameter and is guided into a 1.33 m Czerny-Turner-type spectrometer based on spherical mirrors for collimating and focusing. A charge-coupled device having 13.3ϫ 13.3 mm 2 area size is used as the detector and the spectra from all the lines of sight are recorded perpendicularly to the wavelength dispersion. The spectrometer is equipped with optics located in front of the entrance slit to correct the difference between the meridional and sagittal focal points, and thus the astigmatism, which otherwise causes severe cross talk between adjacent optical fiber images on the detector, is corrected. Consequently, simultaneous spectral measurement with 80 lines of sight is realized. The Zeeman splitting of a neutral helium line, 667.8 nm ͑21 P-3 1 D͒, which is caused by the magnetic field for plasma confinement, is measured with the spectrometer. Though the obtained line profile is in general a superposition of several components on the same line of sight, they can be separated according to their different splitting widths. The two-dimensional poloidal distribution of the helium line intensity is obtained with the help of a tomographic technique.

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“…Because of the requirement for a high spatial resolution it is necessary that the spectrograph be made stigmatic at the operating wavelength. This has been achieved by using the grating in divergent illumination as described previously (Bates et aL, 1970). A spectral resolution of 0.2 A is obtained for an f/15 system with slit widths of 27/2m.…”

Section: Instrumentalmentioning

confidence: 99%